Solid rocket thrust termination device

ABSTRACT

A thrust termination device for terminating solid rocket propellant thrust at a pre-selected point in the rocket trajectory responsive to a signal from an onboard sensing device, to actuate and move a restrainer element out of its blocking position in a resilient and tensioned split ring which thereupon concentrically collapses and compacts to free the rocket motor forward head portion for movement in a thus predictable path, and to enable the extinguishing of the projectile propellant and the termination of rocket thrust, to enable precise range preselection between the points of maximum attainable range and the minimum launch-associated range of the rocket.

United States Patent Long 1 Dec. 12, 1972 1541 SOLID ROCKET THRUST3,122,098 2/1964 Glennan ..60/254 x TERMINATION DEviCE 3,038,303 6/1962Gose ..60/254 [72] Inventor: James A. Long, Wharton, NJ. PrimaryExaminer samuel Feinberg [73] Assignee: The United States of America asAssistant Examiner-James Hanley represented by th secretary of theAttorney-Harry M. Saragovitz, Edward J. Kelly and Army Herbert Ber] [22]Filed: NOV. 2, 1970 57 ABSTRACT [21] PP N04 85,933 A thrust terminationdevice for terminating solid rocketpropellant thrust at a pre-selectedpoint in the [52] us. c1 ..102/49.s, 60/254 mcket "aiecmry Feslmsive asignal fmm an 51 1111.01. ..F42b 15/10, A47f 3/04 ward Sensing devlce,mate and a restrain [58] Field of Search 102/49 4 49 60 I3 5 6 RSelement out of its blocking position in a resilient and 6 tensionedsplit ring which thereupon concentrically collapses and compacts to freethe rocket motor forward head portion for movement in a thus predictable[56] References C'ted path, and to enable the extinguishing of theprojectile propellant and the termination of rocket thrust, to enableprecise range pre-selection between the points 3,177,655 4/1965 White..l02/49.5 of maximum attainable range and the minimum LaPointe launchassociated range of the rocket 3,140,886 7/[964 Cotilla et al...l02/49.5 2,721,517 10/ 1955 Workman ..l02/49.4 4 Claims, 4 DrawingFigures PATENTEBBEB 12 m2 SHEET 2 OF 2 INVENTOR.

A. LONG JAMES BYW SOLID ROCKET TIIRUST TERMINATION DEVICE The inventiondescribed herein may be manufactured, used and licensed by or for theGovernment for governmental purposes without the payment to me of anyroyalty thereon.

BACKGROUND OF INVENTION This invention relates generally to rocketthrust control devices, and more specifically relates to a rocket thrusttermination device, for use with a rocket propelled launch-assistedprojectile, activated pursuant to a signal from an onboard sensingdevice at a preselected trajectory point, which makes possible theprecise and accurate selection of range for such rocket propelledprojectile launched from tube weapons such as mortars.

Pre-selection of range for projectiles fired from tube weapons has beenaccomplished heretofore in general by varying the amount of propellantcharge used or the elevation of the launching tube. Neither of thesemethods is appropriate or useful in the launching of projectiles whereinmost of the propelling energy of the projectile is embodied within theprojectile itself, as in rocket propelled projectiles; in such devices,the greater portion of the projectiles impulse and thrust is impartedafter the projectile leaves the launch tube. In large super-caliberwarhead projectiles, in order to achieve the minimum velocity forprojectile stability because of momentum restrictions, it is desirableand necessary to impart all possible energy within the launch tube. Forsuch projectiles, reducing the propellant charge results in unacceptablylow velocities; also, varying the launch tube elevation within theconstraints of the weapon has little effect on the pre-selection rangezoning. In some instances, thrust deflectors or spoilers may beassembled and added to the projectile to decrease the range; however,these devices severely penalize the accuracy of the round and are alsologistically undesirable because a set of extra parts must be suppliedwith each round and must be selected and assembled in the field. Thepresent invention may be built into the round and set before firing. Itretains all the accuracy inherent in the projectiles design. Also, itpermits the use of fixed launch conditions which can be pre-selected foroptimumassembly, operation and accuracy.

Mortar launched supercaliber warhead projectiles were conceived to giveinfantry the capability to deploy large and heavy warhead systems, butit appeared that they would require additional new apparatus for launchand also would only be capable of limited range use. Standard mortarammunition is light enough to attain sufficient muzzle velocity toachieve long range without imparting excessive recoil momentum to themortar and without excessive breech pressure and may be range zoned byvarying the breech charge to impart various muzzle velocities or byvarying the breech mortar angle of elevation. The new and large heavywarhead projectiles contemplated would require very high breech pressureto attain a useful range and would also impart very high recoil momentumto the mortar, both of which would make a new and much heavier mortarweapon necessary. Even with the new weapon its range would be severelylimited because the large diameter of the warhead carries a highaerodynamic drag penalty,

degrading the velocity imparted by the mortar. The efficiency of such asystem would be rather low. Adding a rocket assist to the projectilesolved some of these problems. The breech pressure and recoil momentumcould be brought down to levels compatible with the tolerable momentumand internal pressure limits of the existing mortar, and the resultingmuzzle velocity would be adequate for initial stability of the rounds.Additional impulse provided by the rocket motor brought the velocity ofthe projectile up to the level required to attain the desired maximumrange. The major problem remaining to be solved was that of preselectedrange zoning. Since the mortars angle of elevation variation is limitedand the maximum mortar breech pressure was being used to provide initialstability for the round, the only degree of freedom permissible wasvarying the impulse imparted by the rocket motor, i.e., terminating thethrust of the rocket motor when sufficient velocity has been imparted tothe round to achieve the desired range. Thus, if the mortar elevationand the mortar propellant charge were kept constant, the basic weaponconditions would be simplified while at the same time if a method toterminate the rocket motor thrust at any given velocity could be devisedthe projectile could be preset to achieve any desired range.

Pursuant to the invention, such pre-selected range zoning for mortarlaunched supercaliber warhead projectiles is provided for by means of anon-board rocket thrust termination device which solves the abovedescribed problems and others, and which has numerous practicalapplications as will be apparent from the disclosure herein to thoseskilled in the art. A piston-restrainer element, interposed between theends of a resilient split ring retainer which in turn is interposedbetween the warhead member and the rocket motor body member in retainingposition, is actuated responsive to a signal from an onboard sensingdevice at a pre-selected range trajectory point, and saidpiston-restrainer is thereby moved out of such position to enablecollapse of said retainer ring, thereby freeing the rocket motor bodymember for movement to cause the extinguishing of the projectilepropellant, to thereby terminate the rocket thrust for precise rangezoning. In one embodiment of the invention, the rocket motor body memberis moved free from the warhead member pursuant to the operation of therocket thrust termination device and separates therefrom, therebyterminating the range assist provided by the propellant and enablingtrajectory preselection. In another embodiment of the invention, therocket motor body member is moved free for movement against an impactabsorbing element within the projectile to enable the onboard venting ofthe propellant to terminate same, to thereby terminate the range assistprovided and to enable non-separation range pre-selection.

In accordance with the foregoing, it may be regarded as among theobjects of the present invention to provide a novel rocket thrusttermination device which is utilized to provide the extinguishing ofrocket assist propellant pursuant to actuation and operation of apre-selected onboard signalled terminating device to thereby enablepre-selected range zoning of mortar launched supercaliber warheadrocket-assist projectiles or other similar projectiles.

BRIEF DESCRIPTION OF DRAWINGS The invention is diagrammaticallyillustrated, by way of example, in the appended drawings wherein similarreference characters indicate like parts, in which:

FIG. 1 is a perspective partly-sectional fragmentary rear view of arocket propelled launch assisted projectile incorporating a thrusttermination device embodying the invention therein;

FIG. 2 is a perspective partly-sectional fragmentary front view of thedevice pursuant to the invention taken on line ll ofFIG. 1;

FIG. 3 is a perspective partly-sectional fragmentary rear view of theseparation of the members in one embodiment of the invention; and

FIG. 4 is an elevational partly-sectional fragmentary side view ofanother embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS In accordance with the preferredmodes of practicing the invention, as shown in the drawings, in oneembodiment of the invention the rocket thrust of a solid rocketpropulsion system, for example, is extinguished by separating theforward bulkhead of the rocket motor from the warhead to therebyextinguish the propellant grain. An onboard sensing device, which senseswhen termination should be accomplished, actuates the mechanism. Thissensing device may comprise, for example, a velocity sensing devicewhich integrates acceleration and actuates the system at anypre-selected velocity, or it may comprise a timer preset to function ata selected time after launch, assuming that the relationship betweentime and velocity has been determined, or it may comprise anothersimilar system. The propellant grain in this embodiment extinguishesimmediately upon separation and the rocket motor will follow behind thewarhead along a predicted path.

In another embodiment of the invention, the propellant grain isextinguished without separating the rocket motor from the warhead, oralternatively if the propellant could be made to burn in such a fashionas to not generate thrust, the same purpose is achieved. Therefore, inthis embodiment the projectile incorporates the thrust terminationdevice so as to permit the rocket motor head to travel forward within anadapter which secures the rocket motor body to the warhead. A cushioningdevice absorbs the forward momentum of the rocket motor body to preventdamage to the warhead. When the rocket motor body moves forward, ituncovers ports in the adapter through which the rocket motor gases aresuddenly vented, thereby extinguishing the propellant grain. Thisembodiment would be useful if the projectile is to be flown over thehead of friendly troops, in which instance if separation were to occuras in the other previously described embodiment, the separated partsmight prove hazardous to our own forces.

In a first embodiment of the invention (FIGS. 1-3) the rocket-propelledlaunch assisted projectile 11 comprises a motor body member 20, warheadmember 21, motor forward head portion 22, motor forward head groove 23,and propellant 24 therein. The thrust termination device 12 positionedin thrust terminator housing 25, comprises, for example, actuation means13, spacer means 14, retention means 15, and cushioning means l6.

The actuation means 13 (FIG. 1) for example, is comprised of an actuatorhousing 30, squib member 31 with charge 32 therein positioned in saidhousing, and lead wires 33 extending therefrom which are connected to anonboard sensing device (not shown).

The spacer means 14 (FIG. 1) comprises, for example, piston housing 40,piston 41 located therewith, locking pin 42 in engagement therewith(FIG. 4), spacer release slide member43 extending thereabout with pistonmovement guide means 44 thereon which comprises, for example, slots 45and bolts 46 (FIG. 2).

The retention means 15 (FIGS. 1, 2 & 3) for example, comprises aretainer ring member 50, with leading ring edges 51; the cushioningmeans 16 comprises cushioning gasket 60 and spacer ring 61 interposedbetween the motor forward head portion 22 and the warhead member 21.

In another embodiment of the invention (FIG. 4), an impact absorbershield which is interposed between the thrust terminator housing 25 andthe warhead member 21 which are affixed together by fixing means 72 andventing apertures 73, are located at surface positions on motor forwardhead portion 22 for venting of said propellant 24.

In operation, in a first embodiment (FIGS. 1-3) for example, the squibmember 31 housed in the actuator housing 30 is fired on actuation of thecharge 32 by a sensing device (not shown) interconnected therewiththrough lead wires 33. The squib member 31, on ignition pursuant to thesignal from the sensing device causes pressure to build up against theface of piston 41 in piston housing 40. This force on the piston 41shears locking pin 42 and causes the piston 41 to move in a generallyupward direction, restrained in its path of movement by piston movementguide means 44 which is located on spacer release slide member 43 whichis affixed for movement with the piston 41. The bottom portion of spacerrelease slide member fits in wedging position between the split ends ofretainer ring member 50, maintaining the ring member 50 in an expandedposition in motor forward head groove 23, thereby retaining the motorbody member 20 and warhead member 21 during firing of the propellant 24.When the pre-selected point of thrust termination is reached, the firingof the piston 41 pulls the spacer release slide member 43 from betweenthe ends of the retainer ring member 50 enabling the ring member 50 tocollapse under its own spring tension plus the compressive load on itfrom the motor head portion. The leading edge of the retainer ringmember 50 may be chamfered so that it collapses concentrically and willnot hang up. Upon collapse of the retainer ring member 50, the pressurefrom inside the rocket motor acting in sequence on the thrust terminatorhousing 25, the retainer ring member 50, and cushioning gasket 60 andspacer ring 61 against the warhead member 21 separates these componentsfrom the motor body member 20 leaving the warhead member 21 in freeflight (FIG. 3). The motor forward head portion 22 experiences amomentary reverse thrust from the opening at the head end facilitatingthe separation from the forward section, and the propellant grain 24snuffs out from the rapid drop in pressure.

The thrust termination is accomplished without separation of the rocketmotor in another embodiment of the invention, shown in FIG. 4. Inoperation in this alternate embodiment, the squib member 31 housed inactuator housing 30 is fired by a signal from a preset on-board sensingdevice (not shown) signalled through lead wires 33 igniting the charge32. On ignition of the squib member 31, pressure is built up against theface of piston 41 in piston housing 40. This force on the piston 41shears locking pin 42 and causes the piston to move in a generallyupward direction, restrained in its movement by piston movement guidemeans 44 on spacer release slide member 43 which is affixed for movementwith piston 41. The bottom portion of a spacer release slide member 43is edged between the split ends of retainer ring member 50, therebyrestraining the ring member 50 in place by wedging it in an expandedposition in motor forward head groove 23 in the motor body, therebyrestraining the motor body member 20 and warhead member 21 during firingof the propellant grain 24. When the pre-selected point of thrusttermination is reached, the firing of the piston 41 pulls the spacerrelease slide member 43 from between the ends of retainer ring member 50causing the retaining ring 50 to collapse under its own spring tensionplus the compressive load on it from the thrust terminator housing 25.The leading edge of the retainer ring member 50 is chamfered so that itcollapses concentrically and will not hang up. At this point thepressure from inside the rocket motor acting in sequence on the thrustterminator housing 25, the retainer ring member 50, and the impactabsorber shield 70, which is maintained in position by the impactabsorber retainer 71, with the warhead member 21 affixed to the motorbody member 20 by fixing means 72, allows the thrust terminator housing25 to move forward, crushing the impact absorber shield 70 against theimpact absorber retainer 71. The movement of the motor forward headuncovers venting apertures 73 in the body which vents the gases from thepropellant grain 24. The rapid venting rapidly lowers the pressure inthe motor and snuffs out the propellant grain thus terminating thrust.

While the present invention has been particularly set forth in terms ofspecific embodiments thereof, it will be evident in view of the instantdisclosure, that numerous variations upon the invention are now enabledto those skilled in the art, which variations in propriety are yetwithin the true scope of this teaching. Accordingly, the invention is tobe broadly construed, and limited only by the scope and spirit of theclaims now appended hereto.

Iclaim:

1. A thrust termination device, for terminating rocket thrust pursuantto a signal from an onboard sensing device, located in a thrustterminator housing, in a rocket propelled launch assisted projectilewhich comprises a motor body member and a warhead member, comprising:

a. termination means, to enable thrust termination at a signalled pointof trajectory, comprising i. retention means which includes, a springtensioned retainer split ring member extending into a groove in themotor forward head portion and therewith said motor body member inengagement with the warhead member in thrusted projectile flight, andspacer means which includes a piston housing, a

piston in said housing, a s acer release slide member affixed to saidpis on for movement therewith, piston movement guide meansinterconnected to said piston for guidance thereof,

and a locking pin frangibly connecting said piston to said pistonhousing, and which in a non-actuated position serves to maintain saidretention means in engagement position.

actuation means which includes, an actuator housing, a squib memberpositioned in said housing with a charge therein, with lead wiresextending therefrom to said onboard sensing device, and which actuatessaid termination means upon a signal from said onboard sensing device tomove said spacer means, out of engagement position with respect to saidretention means, releasing same for movement out of engagement with saidmotor forward body portion groove to enable said motor body member tomove so as to vent said propellant gases to terminate thrust thereby,and

c. cushioning means interposed between said warhead member and saidmotor body member to cushion relative movement of said members on thrusttermination.

2. In a thrust termination device, as set forth in claim 1, saidcushioning means comprising a cushioning gasket and a spacer ring.

3. In a thrust termination device, as set forth in claim 2, saidcushioning means comprising an impact absorber shield, and an impactabsorber retainer.

4. In a thrust termination device, as set forth in claim 3, fixing meanssecuring said warhead member and said motor body member together.

1. A thrust termination device, for terminating rocket thrust pursuantto a signal from an onboard sensing device, located in a thrustterminator housing, in a rocket propelled launch assisted projectilewhich comprises a motor body member and a warhead member, comprising: a.termination means, to enable thrust termination at a signalled point oftrajectory, comprising i. retention means which includes, a springtensioned retainer split ring member extending into a groove in themotor forward head portion and therewith said motor body member inengagement with the warhead member in thrusted projectile flight, andii. spacer means which includes a piston housing, a piston in saidhousing, a spacer release slide member affixed to said piston formovement therewith, piston movement guide means interconnected to saidpiston for guidance thereof, and a locking pin frangibly connecting saidpiston to said piston housing, and which in a non-actuated positionserves to maintain said retention means in engagement position. b.actuation means which includes, an actuator housing, a squib memberpositioned in said housing with a charge therein, with lead wiresextending therefrom to said onboard sensing device, and which actuatessaid termination means upon a signal from said onboard sensing device tomove said spacer means, out of engagement position with respect to saidretention means, releasing same for movement out of engagement with saidmotor forward body portion groove to enable said motor body member tomove so as to vent said propellant gases to terminate thrust thereby,and c. cushioning means interposed between said warhead member and saidmotor body member to cushion relative movement of said members on thrusttermination.
 2. In a thrust termination device, as set forth in claim 1,said cushioning means comprising a cushioning gasket and a spacer ring.3. In a thrust termination device, as set forth in claim 2, saidcushioning means comprising an impact absorber shield, and an impactabsorber retainer.
 4. In a thrust termination device, as set forth inclaim 3, fixing means securing said warhead member and said motor bodymember together.